With the recent box office success of stereoscopic 3D movies, it is desired to bring 3D video to home entertainment, too. One of the first solutions available is the Blu-ray 3D format. Preferably, the 3D movie is displayed inside a so-called comfort zone. Determination of the comfort zone is still an area of active research. Typically, the comfort zone describes an interval in z-space extending from somewhere behind the screen to a minimal distance to a viewer in front of the screen. One option for determination of this comfort zone is the so-called ⅓ diopter rule. Further, the range of the comfort zone according to the ⅓ diopter rule depends on the distance between the viewer or user and the screen. Reproduction of 3D elements outside the comfort zone should be limited to special scenes and should be done with care to avoid user discomfort.
The Blu-ray 3D format not only supports stereoscopic 3D video, it also supports stereoscopic 3D auxiliary information such as stereoscopic 3D interactive applications like a user menu, which are preferably written in the Java programming language.
An interactive menu may allow the user to select a certain scene, a different audio track, etc. Further, 3D subtitles or an information text may be added to the stereoscopic reproduction. Such information, which is typically presented in front of a main video stream, shall be referred to as overlay graphics.
One technical challenge so as to provide a pleasant 3D user experience is to coordinate visual non-video elements, i.e. overlay graphics such as the aforementioned interactive menus, with the main video stream in z-space. In general, so called depth conflicts should be avoided and overlay graphics should be placed in front of the 3D main video stream. Preferably, interactive graphics should be placed in front of the subtitles if possible. A depth conflict between e.g. a main video stream and a user menu occurs if at least parts of both elements take the same place in z-space. In such a conflicting area the user's viewing experience may be unpleasant.
Document WO 2009/083863 A1 discloses a method for display of 3D overlay graphics that are presented in front of a 3D main video stream. In order to prevent occlusions due to depth conflicts the available depth range in z-space is split up into separate sub ranges. A respective sub range in z-space is reserved for overlay data, the main video stream, subtitles, etc.